A symmetrical configuration of second order system is already in use for small high pressure pumps and it would first appear that such system could be used as a rotary internal combustion engine. However, the power required to move the totally unbalanced vanes and the amount of heat losses, due to the friction of the vanes on the casing or stator, are such that the system produces a very small amount of useful power.
Several systems are known where partially unbalanced vanes are used, some of which may be found described in U.S. Pat. No. 1,634,269 issued July 5, 1927, U.S. Pat. No. 1,977,780 issued Oct. 23, 1934, U.S. Pat. No. 2,013,916 issued Sept. 10, 1935 and U.S. Pat. No. 3,642,390 issued Feb. 15, 1972.
These systems use a third order configuration, or trilobic, housing around a circular rotor. Although the centrifugal action on the vanes and the heat losses on the housing may be significantly reduced, the power required to accelerate the double vanes a number of times around the generating circle is such that it precludes the utilization of any of these systems.